Warning for City’s piping network

The City of Cape Town’s best kept secret is the poor state on sections of its bulk water reticulation system and if Day Zero comes it will be because of the collapse of the piping infrastructure, not because we’ve run out of water.

This is the opinion of Brannon Meyer who has extensive engineering experience.

The retired master technician from Tokai worked for the municipality as chief engineering assistant and has a diploma which is the equivalent of a third year B.Sc. Elect. Eng degree.

Mr Meyer believes that the problem is electrolytic corrosion.

Devices called sacrificial anodes are fitted at various locations along the bulk pipeline. Many domestic geysers have them and if they are not checked regularly and replaced, the hot water cylinders could burst.

Industrial size sacrificial anodes, however, weigh between 20kg and 25kg each and about 60 of them have been installed on the bulk piping that criss-crosses Cape Town.

“If you leave a piece of steel exposed to the elements, it will erode; if you put it into the ground containing various minerals, it will erode faster and if you put it into water with salt and other minerals, it will erode even faster.

“The moisture and specific minerals in the ground and the salt in the water form an electrolyte and react with the steel as in a water pipeline, to form a local cell, like a mini motor car battery, causing a circulating current and this accelerates the corrosion process even more,” Mr Meyer explained.

He said the sacrificial anodes were installed at 60 locations “to stop accelerated corrosion on sections of the bulk water supply pipeline. Some systems had to be inspected and electrical measurements taken twice yearly and others monthly to ensure the systems were functioning and to timeously replace sacrificial anodes, and components to negate electrolytic corrosion”.

Before he retired Mr Meyer did essential tests and regular inspections at 60 sites to check that the anodes and not the pipelines were being eroded. However, he believes that regular testing and inspections have long since stopped.

Last year, in reply to a letter in the Constantia Bulletin (July 27, 2017), published by Cape Community Newspapers, Xanthea Limberg, mayoral committee member for informal settlements, water and waste services; and energy, said the tests and inspections were no longer being done due to vandalism of the systems, and the systems would be reinstated by an external service provider over the next few years.

In a follow-up, the City’s media team confirmed that the anodes had not been checked for 10 years.

“These tests were previously an in-house function which concerns me more. Now for at least 10 years, the bulk water pipeline has been subjected to accelerated corrosion. According to Ms Limberg, this ‘reinstatement’ would be done ‘over the next few years’, but this could be as long as a piece of string,” Mr Meyer said.

“I hope you can get a more detailed answer otherwise soon we will be paying a pipeline levy.”

Ms Limberg said given that the City’s current focus is on more urgent drought-related interventions, including safeguarding existing supply and delivery of additional water, performing further repair and maintenance of the cathodic corrosion protection systems has not been possible.

“It is highly unlikely that large numbers of catastrophic pipeline failures would occur as there are other corrosion protection measures in place. These include cement sheathings around pipelines and paint coatings on the accessible valves and fittings. During frequent work on our pipelines and other infrastructure, we have not observed areas of extensive steel loss due to corrosion. Any leaks detected are immediately repaired to prevent water loss.

“We have made large strides in the past decade to progressively reduce water losses. Repair processes have been streamlined, and a focus on preventative maintenance has reduced the burst rate from 63.9 bursts per 100km of piping in the 2010/2011 financial year to below 30 bursts per 100km according to most recent figures. Cape Town has the lowest non-revenue water figures of major municipalities in South Africa. As a City, our overall water losses is 16% versus the national average of 36%,” she said.

However, Ms Limberg did not answer any of my questions including: what contingency plans does the City have in place should there be 60 bursts along sections of the bulk water supply pipeline near Cape Town?

And, how many kilograms of steel have been eroded at each of the 60-odd locations over the last 10 years?

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